The present invention relates to an improved actuator for water heating/cooling and sanitary systems, according to the preamble of claim 1.
In the heating and sanitary system field, so-called xe2x80x9cthermoelectricxe2x80x9d shutters, including a substantially thermoexpansible element, for example a wax capsule which, as it passes from a solid to a molten status thereof, upon a heating operation, expands to cause a valve, manifold or the like shutter, to be driven from a closing position to an open position and vice-versa are already known.
Said prior thermoelectric actuators have, due to a corresponding small size of their expanding material capsules, a small size, thereby they can be assembled both on individual components, such as valves, and on manifolds including a plurality of shutters typically spaced with a pitch of or less than 50 mm.
However, while said prior actuators reliably operate in their opening/closing operations, they are affected by several drawbacks and disadvantages. At first, their shutter can be exclusively driven to open/closed positions, thereby preventing a continuous adjustment of the flow rate through the circuit coupled to said shutter. This would involve a low operating efficiency, for example in water heating/cooling systems, with a consequent large power consume and heating cost.
In fact, a single opening/closing mode of operation; cannot provide an optimal adjustment, for example, of the water heating/cooling system to provide said system with the required operating flexibility, as could be achieved by modern available digital technologies, such as fuzzy logic, autotuning, and so on techniques.
Moreover, the heating of the wax material melting resistive element, requires a comparatively great current drain: for example, a manifold including 15 actuators would require a comparatively high power consume and related cost, and a wiring including wires having a correspondingly large cross-section.
A further drawback of prior thermoelectric actuators is that they have a comparatively long switching on time, thereby a large electric power is consumed for heating and melting the wax material. In particular, after a long off period, for example at the start of the heating/cooling season, said switching on time would amount to 8-10 minutes, whereas, in the operation of the heating/cooling system, this time would amount to 4-5 minutes, with great variations depending on the environment conditions. Since the power drain of a prior thermoelectric actuator is of about 5W, and since, for multiple actuators, for example 15 and more in manifold arrangements, said power drain proportionately increases, said prior thermoelectric actuators cannot be battery power supplied. Furthermore, said prior actuators must overcome the overlapping shutter resilient forces, for example of 15 Kg, thereby preventing said prior thermoelectric actuators from being replaced by newly designed low cost actuators, suitable to replace said prior thermoelectric actuators, which are large series products.
For larger size circuit valves, i.e. for comparatively large flow-rate circuits, so-called xe2x80x9celectricxe2x80x9d actuators are moreover known, which comprise an electric motor, such as a synchronous motor or a step motor, which electric actuators, however, have a large size and a great electric drain, a motor-reducing unit being sometimes arranged between their motor and shutter. The overall size of this prior electric actuators, on the other hand, is comparatively large, thereby they cannot be properly miniaturized to efficiently replace said prior thermoelectric actuators.
Furthermore, the electric actuators comprise many components and have a rater high cost; thus they cannot be used in water heating/cooling and sanitary system manifolds including spaced-apart shutters; this increased size, moreover, would negatively affect the installation of the mentioned components.
While the requirement of replacing prior thermoelectric actuators by other types of actuators allowing a continuous adjustment of the driven shutter controlled flow rate, while providing a less switch-on time, is well known in this field since 20 years, alternative actuators suitable to meet the above mentioned requirements have not been yet provided.
Accordingly, the aim of the present invention is to provide an improved actuator, of the above mentioned type, which, on a side, is free of the drawbacks and disadvantages of prior actuators and, on the other side, allows to perform a continuous adjustment of the shutter movement or stroke, while providing a very reduced switch-on time and electric drain.
Within the scope of the above mentioned aim, a main object of the present invention is to provide such an actuator construction which is very reliable in operation and has a long life, and can be made at a cost substantially like that of prior thermoelectric actuators.
According to one aspect of the present invention, the above mentioned aim and objects, as well as yet other objects, which will become more apparent hereinafter, are achieved by an improved actuator for water heating/cooling and sanitary systems, having the features of claim 1.
Further improvements and advantageous embodiments are defined in the dependent claims.
The improved actuators according to the invention provide a lot of advantages. The use of a D.C. motor provides an optimum size/torque ratio, with a time consistent operation fully independent from the environment conditions. Moreover, since miniaturized D.C. low power motors, like those provided by the invention, are at present used in a very large series in the motor vehicle industry, they can be made at a very low cost. The high RPM of the D.C. motors is advantageously herein greatly reduced by a reducing unit which can be easily made from plastics materials, is noiseless and provides a reduction larger than 1000 with its diameter less than 15 mm, i.e. substantially equal to the diameter of a suitable miniaturized D.C. motor, thereby providing the desired and necessary small size for assembling on conventional manifolds having shutter pitches less than 50 mm. A further advantage is that of transforming, by a worm screw, the rotary movement of a planetary reducing unit into an axial reciprocating movement thereof, thereby further increasing the reduction ratio, on a side, and allowing said actuator, on the other side, to reliably drive shutters requiring high driving forces, for example larger than 15 Kg. A further advantage of the above mentioned miniaturized D.C. motors is the very low power drained thereby, of about 8 times less than that of prior thermoelectric actuators, affected by the above mentioned limits. This low consume feature, in addition to being advantageous from the power drain aspect, makes the actuator driven by a miniaturized D.C. motor very suitable for battery power supply arrangements.
Yet another advantage of the improved actuators according to the present invention is that, by properly adjusting the shutter displacement, it is possible, by using known digital timing methods, to provide very high efficiency heating/cooling systems, depending on the user requirements, through the overall operation day. The required displacement or stroke variations are achieved in a very short time and reliable manner, in opposition to a 4-5 minute opening/closing switching time of prior thermoelectric actuators, and with an operation which is fully independent from the contingent requirement conditions. Moreover, the power drain is further limited by the fact that the switching on time of the motors can be reliably controlled by an easily constructed electronic card. Yet another advantage is that the invention uses a mechanical clutch preventing the motors from locking at their end of stroke positions, which, together with a reliable timing by the control electronics, provides the actuator with a long operating life, i.e. greater than 10 years. A further advantage is that the provided planetary reducing unit can be assembled in an automatic manner, thereby reducing the assembling time and, accordingly, the overall making cost. Yet another advantage is that a plurality of adapters are provided, allowing to assemble a respective actuator according to the invention on different types of existing manifolds.